mm/debug: sync up latest migrate_reason to migrate_reason_names

Sync up MR_DEMOTION to migrate_reason_names and add a synch prompt.

Link: https://lkml.kernel.org/r/20210921064553.293905-3-o451686892@gmail.com
Fixes: 26aa2d19 ("mm/migrate: demote pages during reclaim")
Signed-off-by: Weizhao Ouyang <o451686892@gmail.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mina Almasry <almasrymina@google.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Wei Xu <weixugc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/migrate.h

@@ -19,6 +19,11 @@ struct migration_target_control;
  */
 #define MIGRATEPAGE_SUCCESS		0
 
+/*
+ * Keep sync with:
+ * - macro MIGRATE_REASON in include/trace/events/migrate.h
+ * - migrate_reason_names[MR_TYPES] in mm/debug.c
+ */
 enum migrate_reason {
 	MR_COMPACTION,
 	MR_MEMORY_FAILURE,
@@ -32,7 +37,6 @@ enum migrate_reason {
 	MR_TYPES
 };
 
-/* In mm/debug.c; also keep sync with include/trace/events/migrate.h */
 extern const char *migrate_reason_names[MR_TYPES];
 
 #ifdef CONFIG_MIGRATION

mm/debug.c

@@ -26,6 +26,7 @@ const char *migrate_reason_names[MR_TYPES] = {
 	"numa_misplaced",
 	"contig_range",
 	"longterm_pin",
+	"demotion",
 };
 
 const struct trace_print_flags pageflag_names[] = {